Disruption/rehoming question?

So I've been asked for input on a situation and honestly don't have a lot in terms of legalities--thought I would throw it out and see what others have to say before I get back to them. I've been put in contact with a father of six children, all of whom have been adopted. A few weeks ago the wife apparently decided she didn't want to be a mom any more and walked out on the family. The odds that she will come back or want anything to do with the children in terms of visitation/support are slim. The older 3 children already have emotional issues, and are acting out/in (either anger or depression) in response to the situation. The father feels the youngest three are at risk of being overlooked, at best, and victimized by the older children at worst. They are 6, 4, and 2 1/2 and they just finalized on the two youngest 7 months ago (they were adopted out of foster care, the 6 year old was adopted privately). There is no support from extended family on either parents' side. He is pretty isolated apparently, aside from some support from his church group, but nobody who understands the complexity of dealing with children with emotional issues--from what has been described I would guess at least one of the three older children has RAD (perhaps mom didn't just "walk out" but was driven out?). He has asked about the possibility of placing the 3 younger children in another adoptive family privately. Does anyone know what legalities are involved in finding a private placement for children who were previously adopted, particularly through the foster care system? We are in UT if that makes a difference. I know my input off the top of my head would be to be cautious about making any decisions this soon after a transition when the family is still in crisis...but if the kids are at risk staying at a home where there are older, emotionally unstable children it may be the best option!